Passively Deployed Lightweight Solar Array Structure for Thinned-Multijunction Solar Cells

Current deployable solar array systems are based on designs that have been in existence for more than 30 years. In general, these heritage designs can be divided into two classes: 1) hinged-panel arrays, which are mechanically simple but mass inefficient, and 2) tensioned-membrane arrays, which are mechanically complex but mass efficient. Arguably, no deployable solar array designs exist that are both mechanically simple and mass efficient. Furthermore, the largest heritage systems (i.e., tensioned-membrane arrays) are limited to less than 15 kW of total power and 50 W/kg of specific power. Higher power generation capability (i.e., greater than 50 kW) with efficient packaging (i.e., greater than 250 W/kg) is becoming an important requirement for many future Air Force missions. GaAs-based multi-junction solar cells can now be thinned (below 20 microns-thick) in order to produce flexible solar cells of the same efficiency as current, much thicker, state-of-the-art rigid solar cells. If these thinned cells are integrated onto next-generation, ultra-lightweight, deployable solar array structures that exploit the novel design characteristics of the cells, 6 fold improvements to the specific power (>500W/kg) of space deployable solar arrays can be attained in the near term for systems up to 100kW in size. Thin, flexible-cell arrays offer a potential solution to the above challenges, as they are capable of more compactly stowing for launch, while having a lower mass than traditional arrays. Unfortunately, the benefits attained by populating array structures derived from heritage deployable technologies with these thin, flexible-cells are not sufficient. In order to achieve the desired power output and specific power goals for next-generation solar power systems, lightweight solar array structures must also be designed and optimized for the new thin cell technologies. These lightweight solar arrays must provide significant advances upon the specific power of the array, while still retaining the stiffness requirements for launch and on-orbit attitude control maneuvers.